a) Basic Terminology:
Disk drive: provide computer host system with block data through special cable access such as IDE or SCSI cable depends on type of disk drive.
SAN: a storage system comprises one or multi-disk drives and provides computer host system with block data through fiber optical for fiber channel accessing or Ethernet cable for TCP/UDP/IP accessing.
NAS: a dedicated storage system, which comprises one or multiple disk drives and configured to provide specialized file system services to end user system through network so that the end user system can provide service such as file service, web service, video service etc. based on the file system that looks like a local mounted file system on the end user's system, yet it is actually provided by the NAS.
b) The Traditional Server:
Currently there are two types of servers on the market one is SMP based and another is MPP based.
SMP Based Server:
This type of system has one operating system (OS) running on top of multiple processors (CPU). Each processor may need to compete certain system resources with other processor in order to perform a task. Therefore, it may introduce certain delay for each processor to execute a task.
MPP Based Server:
Other conventional servers utilize multi-node massively parallel processor (MPP) machines including a clustering together of processors that do not share resources such as memory (i.e., each CPU has its own memory). Each processor has its own operating system (OS) or part of OS. Though the CPUS do not share common memory, the node may commonly support a distributed file system on top of a group of nodes, wherein the contents are stored on the file system. This requires complex coordination between the nodes through intra-node communication channel. Hence, this will introduce delay in term of task executing by a processor. Even there is MPP clustering system do not support distributed file system, each processor on the system often still support coordinate each other to perform a portion of the task.
All of these types of servers are very expensive and geometrically limited in a centralized location. In addition, the current the servers on internet such as web server, proxy server, and web cache server are not intelligent enough such that they do not provide automatic fault handling hence they do not have the concept of virtual server.
While these servers may still serve different computational purpose, there are many tasks, which these server may not perform efficiently such as deliver video on internet etc, deliver the block data to host etc cross corporate intra-net and internet. There is, therefore, a need for powerful and inexpensive server, which can distribute the computing power cross intra-net or internet, provides scalable capacity, high performance, yet still provide intelligent automatic fault handling, and security etc.